1. Field of the Invention
The present invention relates generally to a protective device assembly, and particularly to a cover assembly for a heat dissipation device to protect thermal interface material spread on the heat dissipation device from contamination, and to protect fasteners of the heat dissipation device from dropping out thereof, before the heat dissipation device is assembled to a CPU or CPU module.
2. Description of Related Art
Electronic devices such as central processing units (CPUs) generate a lot of heat during normal operation. If the heat generated by the electronic devices is not properly dissipated, it can deteriorate their operational stability and damage associated electronic devices. Thus the heat must be quickly and efficiently removed to ensure the normal operation of these electronic devices. A heat dissipation device is often attached onto a top surface of a CPU to remove heat therefrom. The heat dissipation device is secured to a board by fasteners, wherein the CPU is mounted on the board. Gaps inevitably exist between the heat dissipation device and the CPU and hence causes reduction of heat transferring efficiency from the CPU to the heat dissipation device due to poor heat-transmission through air in the gaps. To ensure intimate contact between the CPU and the heat dissipation device, a layer of thermal interface material is usually spread on a heat absorption surface of a heat sink to improve heat-transmission between the heat sink and the CPU. The heat generated by the CPU causes the thermal interface material to become more liquid, enabling the thermal interface material to fill in the air gap formed between the heat sink and the CPU, thereby improving heat-transmission efficiency between the heat sink and the CPU.
However, the thermal interface material cannot be applied to the heat sink in advance since it is not solid at room temperature and may contaminate surrounding articles or be contaminated by dust or foreign particles before the heat sink is attached to the CPU. To overcome the above problem, various protective devices have been developed. The protective devices are attached onto a bottom surface of a heat sink to enclose the thermal interface material spread on the bottom of the heat sink. The thermal interface material thus cannot be contaminated by dust or foreign particles, and does not contaminate surrounding articles when the heat sink is transported or handled. By using the protective device, the thermal interface material can be applied to the heat sink in advance, thereby simplifying the process of attachment of the heat sink to the CPU. However, the protective device covers the whole bottom of the heat sink, thereby being prone to be loosened from the bottom portion of the heat sink during transport. Furthermore, the protective device needs to enclose parts of the heat sink which do not have a layer of thermal interface material, thus wasting the material for forming the protective device.
Moreover, the protective device just covers on the bottom of the heat sink. The fasteners for securing the heat sink to the printed circuit board extend through a lateral side of the heat sink, which are not covered by the protective device; the fasteners are easily to drop from the heat sink when the heat dissipation device is transported.
What is needed, therefore, is an improved protective device assembly which can overcome the above problems.